TRI-N-BUTYLPHOSPHATE CO2 AND ACETONE/CO2 PHASE BEHAVIORS AND UTILITIES IN CAPILLARY SUPERCRITICAL-FLUID CHROMATOGRAPHY/

Because the phase behavior of the mobile phase must be known before co nclusions fr-om supercritical-fluid chromatography (SFC) can be consid ered reliable, the phase behaviors of tri-n-butylphosphate/CO2 and ace tone/CO2 were thoroughly determined in a variable-volume view cell at conditions applicable to SFC (0-20 mol % modifier, 25-140 degrees C, a nd 80-415 atm). The chromatographic utilities of the binary fluids wer e determined with test compounds (condensed tannins and steroids). Alt hough the UV-absorbance detector base-line rise was severe with aceton e/CO2, chromatographic performance was not compromised. Standard base- line correction methods were used to produce conventional-looking chro matograms. The chromatographic performance with tri-n-butylphosphate/C O2 was unsatisfactory (erratic retention). Static restrictors (integra l, frit, crimped Pt/Ir, linear, and valves) produced erratic flow. Hea ting the restrictors to 250-400 degrees C did not improve performance. Reasons for the compromise in chromatographic performance are propose d.